The expression “vinyl chloride polymer”, abbreviated to “VCP” here and hereinafter, designates vinyl chloride homopolymers, vinyl chloride copolymers, and also mixtures of the above polymers. In particular, the expression “VCP” covers                polyvinyl chlorides (PVC) produced via homopolymerization of vinyl chloride, and        vinyl chloride copolymers which are formed via polymerization of vinyl chloride with one or more comonomers, such as ethylene, propylene, or vinyl acetate.        
The expression “film” here and hereinafter covers separate pieces of a film, and also industrially produced film webs with lengths of from some hundreds of meters up to some thousands of meters.
The film of the invention is produced by plastifying and then extruding a mixture comprising vinyl chloride polymer, polyester, and additives—hereinafter termed VCP mixture—through a die, or by calendering, and can be further processed inline and/or offline. The film is particularly suitable for thermoforming complex-shape packaging.
Polyester films and VCP films are known in the prior art.
The patent EP 1 066 339 B1 (whose United States equivalents are U.S. Pat. Nos. 6,551,699 B1 and 6,068,910) of Eastman Chemical Company (Tennessee, USA) describes a process for producing a film or a sheet made of a polyester resin composition by calendering. The polyester component of the resin is an amorphous or semicrystalline polyester which has a crystallization halflife time of at least 5 min from the molten state. The polyester component or the polyester is one selected from polyesters composed of (i) diacid moiety components and (ii) diol moiety components. The polyester here is composed of (i) at least 80 mol % of a diacid moiety component selected from terephthalic acid, naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, isophthalic acid, and mixtures thereof, and (ii) from 80 to 100 mol % of a diol moiety component selected from diols having from 2 to 10 carbon atoms and mixtures thereof and from 0 to 20 mol % of a modifying diol selected from 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 2,24-trimethyl-1,3-pentanediol, propylene glycol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol; where the diacid moiety component is based on 100 mol % of diacid moiety and the diol moiety is based on 100 mol % of diol moiety. The resin composition of EP 1 066 339 B1 also comprises an additive which is an internal lubricant or antislip agent, or a mixture thereof. The amount added of the additive is from 0.01 to 10% by weight, based on the total weight of the resin composition. Amorphous or semicrystalline polyester resin compositions have good suitability for conventional calendering processes. Films or sheets of uniform shape can be produced via calendering of polyester resin compositions of this type. The polyester resin compositions are marketed by way of example as CADENCE® by Eastman Chemical Company. They are usually used as main component for producing polyester films, where their proportion, based on the total weight of the polyester films, is generally above 96% by weight.
VCP films are produced from VCP compositions or VCP mixtures which respectively comprise various additives or modifiers which give the films a particular property profile. The prior art discloses VCP mixtures or VCP films which are respectively deformable when heated and are suitable for a wide variety of applications, for example as packaging films, shrink films, and rigid films. With the aim of influencing the properties of VCP films in a controlled manner, additives are added in order to increase impact resistance and heat resistance, processing aids are added in order to improve processability and production plant output, lubricants are added in order to improve gelling behavior during manufacture, matting agents are added to reduce gloss, and in particular flow aids are added in order to improve thermoformability and orientability. The proportions by weight of the individual additives depend on requirement and are from 0.1 to above 40% by weight. In order to improve the flowability, the thermoformability, and the orientability of VCP mixtures it is preferable to use amounts of at least 5 to more than 50% by weight of vinyl chloride copolymers. Further additives used comprise polymers of acrylonitrile-butadiene-styrene, methyl methacrylate-butadiene-styrene, methyl methacrylate-acrylonitrile-butadiene-styrene, methyl methacrylate and chlorinated polyethylene, polymethyl methacrylate and ethylene-vinyl acetate as impact-resistance components in an amount of from 1 to 20% by weight, based on the weight of the VCP film. VCP mixtures for films use conventional lubricants, e.g. fatty acids, fatty alcohols, fatty acid amides, metal soaps, esters of fatty acids with mono- or polyhydric alcohols, esters of dicarboxylic acids with mono- or polyhydric alcohols, esters of fatty acids and dicarboxyolic acids with polyhydric alcohols, the materials known as mixed esters or complex esters, esters of phthalic acid with mono- or polyhydric alcohols, or natural or synthetic waxes. The amount of lubricants is from 0.1 to 2% by weight, based on the total weight of the VCP mixture. Known heat stabilizers are organotin stabilizers, in particular tin carboxylates, tin mercaptides, and tin thioglycolates. It is also possible to use metal stabilizers based on calcium and zinc, and other metal-free organic stabilizers, and inorganic stabilizers, for example chlorine scavengers based on dihydrotalcite. The proportion of heat stabilizers is generally from 0.3 to 5% by weight, based on the total weight of the VCP mixture.
However, the use of vinyl chloride copolymers as flow aids in order to improve the thermoformability and orientability of PVC films or of VCP films reduces thermal stability, increases the tendency of the plastified VCP mixture to stick, and reduces the heat resistance of the films produced therefrom. These disadvantageous effects are known and are compensated by using complex additive formulations which are attended by considerable logistics cost in manufacturing.